Mass does not change anywhere in the space .
So the given 30N is equal to the product of mass of the body and the acceleration due to gravity at that place in space.
After finding the mass of the body multiply it by the given acceleration due to gravity.
Mg is the approximate force due to gravity between the mass and the planet.
I hope this may help you.
THere is a standard relationship that gives this result where the capacity of the capacitor is used:

.
We know though that Q/c=V and thus we can use the relationship:
E=Q*V/2 where we have just substituted in. If we also take into account that Q=VC, we can also get that E=V^2*C/2.
We are given the charge and the potential, so the best expression to use is the middle one.
Substituting, we get that E=1/2*8*10^(-10)*20=8*10^(-9).
The answer is B
The answer is B hope this helps
To find out the weight of the object, you'll need to slide the weight poises until the pointer is at zero again. Start with the two heavier weight poises and then use the lightest one to do the fine tuning. Our triple beam balance and the Ohaus triple beam balance are accurate to 0.1 grams.